Vacuum pump

ABSTRACT

Vacuum pump having a housing which defines a pump chamber and a drive chamber. A rotor is arranged in the housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet. Therein, the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber. The shaft feedthrough has a connection, wherein the connection is connected to an underpressure, so that a barrier gas flows from the drive chamber at least partially through the shaft feedthrough to the connection.

CROSS-REFERENCE OF RELATED APPLICATION

This application is a Section 371 National Stage Application of International Application No. PCT/EP2021/073450, filed Aug. 25, 2021, which is incorporated by reference in its entirety and published as WO 2022/043357 A1 on Mar. 3, 2022, the content of which is hereby incorporated by reference in its entirety and which claims priority of German Application No. 20 2020 104 945.3, filed Aug. 26, 2020.

BACKGROUND

The present invention relates to a vacuum pump and a vacuum pump system.

Known vacuum pumps have a housing with an inlet and an outlet. At least one rotatably mounted rotor is arranged in the housing, wherein the rotor has at least one rotor element arranged in a pump chamber formed by the housing for conveying a gaseous medium from the inlet to the outlet. Therein, the rotor extends in the housing from the pump chamber through a shaft feedthrough into the drive chamber. For example, a transmission, a belt drive, an electric motor or the like can be arranged in the drive chamber. The drive chamber is usually at atmospheric pressure. However, since the pressure at the outlet of the vacuum pump is usually higher than atmospheric pressure for conveying the gaseous medium against the atmosphere, process gases from the pump chamber can also enter the drive chamber and escape from there into the environment, provided that said drive chamber is not additionally sealed against the atmosphere. Said escaping is undesirable and must be prevented, particularly in processes in which process gases that are hazardous to health and/or environmentally harmful are conveyed through the vacuum pump.

For this purpose, it is known to provide shaft seals on the shaft feedthrough. They can effectively prevent process gases from escaping from the vacuum pump without barrier gas, provided that the shaft seals are designed as contact seals. However, this necessitates frictional power and, due to wear with advancing service life, such contact seals become leaky and have to be replaced as part of maintenance. As an alternative to known contact seals, shaft seals with a barrier gas are known. In this case, a permanent gas supply at a pressure above atmospheric pressure is applied to the drive chamber, resulting in a continuous gas flow from the drive chamber into the pump chamber. The escape of a process gas is avoided due to this flow direction. However, the permanent gas supply leads to increased installation and operating costs. In particular, such a solution is not accessible if no compressed air is available at the installation site of the vacuum pump.

The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.

SUMMARY

The problem addressed by the present invention is that of creating a vacuum pump in which an escape of a process gas is efficiently prevented by simple means.

The problem is solved by a vacuum pump according to claim 1 and a vacuum pump system according to claim 11.

The vacuum pump according to the invention has a housing which defines a pump chamber and a drive chamber. A rotatably mounted rotor is arranged in the housing, wherein the rotor has at least one rotor element for conveying a gaseous medium from an inlet to an outlet. In this case, the rotor element is arranged in the pump chamber. Furthermore, the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber. For example, a transmission, a belt drive and/or an electric motor can be arranged in the drive chamber in order to set the rotor in rotary motion. In particular, the shaft feedthrough is arranged at the outlet-side end of the rotor in the region of high pressures or at the end of the rotor opposite the inlet. According to the invention, the shaft feedthrough has a connection, wherein the connection is connected to an underpressure, so that a barrier gas flows from the drive chamber at least partially through the shaft feedthrough to the connection. Due to the underpressure, air is thus suctioned from the drive chamber through the shaft feedthrough. Due to the flow direction from the drive chamber to the shaft feedthrough, no process gas can reach the drive chamber in the opposite direction from the pump chamber. In particular, the barrier gas is ambient air. In particular, the barrier gas does not have to flow through the entire shaft feedthrough. It is sufficient that the barrier gas flows from the drive chamber only through part of the shaft feedthrough and is then suctioned toward the connection due to the underpressure. This corresponds precisely to the reverse flow direction of the barrier gas between the drive chamber and the connection when compared to the prior art. It is therefore not necessary to provide a compressed air connection in order to generate a pressure above atmospheric pressure in the drive chamber.

Preferably, a pressure P₁ prevails in the drive chamber, wherein P₁ in particular corresponds to the atmospheric pressure, since the drive chamber is connected in particular with the environment. Furthermore, the underpressure at the connection has a pressure P₂, wherein P₂<P₁ applies. Due to this pressure difference between the drive chamber and the underpressure, the barrier gas flows from the drive chamber in the direction of the connection and thus prevents a process gas from escaping into the drive chamber.

A pressure P₃ preferably prevails in the pump chamber at the shaft feedthrough or in the region of the shaft feedthrough. In particular, pressure P₃ is in this case greater than the atmospheric pressure for conveying the process gas against the atmosphere. The underpressure also has a pressure P₂ as mentioned before, wherein P₂<P₃ and in particular P₃≤P₁>P₂ applies.

The connection is preferably connected to a vacuum pump in order to generate the underpressure, in particular with a pressure P₂. Only a small conveying capacity of this vacuum pump is required and the vacuum pump for generating the underpressure P₂ can be designed to be small and inexpensive.

The connection is preferably connected to a vacuum portion of the pump chamber for generating the underpressure. As a result, the underpressure required at the shaft feedthrough is generated by the vacuum pump itself, so that no further vacuum pump is required. In particular, the vacuum portion of the pump chamber corresponds to the inlet of the vacuum pump. As a result, a sufficient underpressure is generated at the connection of the shaft feedthrough for generating a flushing gas flow from the pump chamber to the connection of the shaft seal.

A first throttle is preferably arranged between the drive chamber and the connection of the shaft feedthrough. The first throttle restricts a gas flow from the drive chamber through the connection. In particular, if the connection is connected to a vacuum portion of the pump chamber, the first throttle reduces a conveying of gas from the drive chamber and thus an associated power reduction of the vacuum pump.

The first throttle is preferably formed by a first portion of the shaft feedthrough. In this case, the first throttle is designed in particular as a non-contact shaft seal, for example, formed by one or more of a piston ring seal, a labyrinth seal, a sealing gap between the rotor and the housing, and a conveying thread on the rotor and/or the housing. This creates a contact-free shaft feedthrough which is particularly low in maintenance.

A second throttle is preferably arranged between the pump chamber and the connection. The second throttle restricts the gas flow between the outlet of the vacuum pump and the vacuum portion of the pump chamber, in particular the inlet of the vacuum pump. The second throttle thus ensures that as little process gas as possible reaches the vacuum portion of the pump chamber, or has to be conveyed by the further vacuum pump, through the shaft feedthrough and the connection.

The second throttle is preferably formed by a second portion of the shaft feedthrough, wherein the second portion of the shaft feedthrough is designed in particular as a contact-free shaft seal, for example, including a piston ring seal, a labyrinth seal, a sealing gap between the rotor and housing, or a conveying thread on the rotor and/or the housing.

The present invention also relates to a vacuum pump system having a first vacuum pump and at least one second vacuum pump. In this case, each of the pumps has a housing which defines a pump chamber and a drive chamber. Furthermore, a rotor is arranged in the respective housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet of the respective vacuum pump. In this case, the respective rotor extends from the pump chamber through a shaft feedthrough into the drive chamber. In this case, the respective shaft feedthroughs have a connection, wherein the connection is connected to a common inlet of the first vacuum pump and the at least second vacuum pump. Alternatively, the respective connections are connected to a further, in particular common, vacuum pump for generating an underpressure at the connection, so that one barrier gas each flows from the respective drive chamber through the respective shaft feedthrough.

The outlet of the first vacuum pump is preferably connected to the inlet of the second vacuum pump for the serial arrangement of the vacuum pump. The inlet of the first vacuum pump thus represents the common inlet of the first vacuum pump and the second vacuum pump.

Alternatively, the inlet of the first vacuum pump is preferably connected to the inlet of the at least one second vacuum pump, and the outlet of the first vacuum pump is also connected to the outlet of the at least one second vacuum pump for the parallel arrangement of the vacuum pumps. For this purpose, the respective inlets of the vacuum pumps are connected to form a common inlet.

A check valve, which closes when the pressure in the respective vacuum pump is higher than at the common inlet, is preferably arranged between each vacuum pump and the common inlet. This prevents the occurrence of a backflow through one of the vacuum pumps. In particular, if one of the vacuum pumps were to be switched off and is not conveying, the check valve closes, so that no gas flow occurs through the deactivated vacuum pump from the outlet to the inlet.

The Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detail Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail using preferred embodiments with reference to the accompanying drawings.

In the drawings:

FIG. 1 shows a vacuum pump having a shaft seal according to the prior art;

FIG. 2 shows a vacuum pump having a shaft seal according to the present invention in a first embodiment;

FIG. 3 shows a vacuum pump having a shaft seal according to the present invention according to a second embodiment;

FIG. 4 is a detailed view of the shaft feedthrough; and

FIG. 5 shows a vacuum pump system according to the present invention.

DETAILED DESCRIPTION

FIG. 1 shows the prior art with a vacuum pump 10 having an inlet 12 and an outlet 14. The vacuum pump 10 has a housing, wherein the housing defines a pump chamber and a drive chamber. A rotor rotatably mounted in the housing extends in this case from the pump chamber into the drive chamber through a shaft feedthrough 16. This is shown schematically in FIG. 1 . In this case, a connecting point 19 is arranged in the pump chamber, whereas a connection point lies in the drive chamber 20. In the drive chamber 20, a pressure P₁ usually prevails, which corresponds to atmospheric pressure due to the connection between the drive chamber 20 and the environment.

In this case, the shaft feedthrough 16 has a connection 18 via which the shaft feedthrough 16 is connected to a compressed air source 22 according to the prior art. The compressed air source 22 supplies compressed air at a pressure P₂′. Furthermore, a pressure P₃ prevails at the outlet 14 of the vacuum pump 10, which is usually higher than atmospheric pressure, so that the vacuum pump 10 can convey against the atmosphere. Due to the compressed air made available, P₂′>P₃>P₁ applies. Therefore, compressed air flows as barrier gas from the connection 18 into the drive chamber 20 and to the outlet 14 of the vacuum pump 10, as indicated by the arrows in FIG. 1 . Due to the flow of the flushing gas from the connection 18 to the outlet 14 of the vacuum pump 10, no process gas passes through the shaft feedthrough 16 into the drive chamber 20 in the direction opposite to the flow direction of the flushing gas. For this purpose, a first throttle 26 and a second throttle 24 are provided in the shaft feedthrough. A suitable design of the first throttle 26 and the second throttle 24 ensures that the barrier gas essentially reaches the connecting point 19, thus providing an adequate supply of the flushing gas. However, in the prior art, it is necessary to continuously supply the shaft feedthrough 16 with compressed air at the compressed air connection 22, so that P₂′>P₃ always applies. This leads to increased operating costs and such a solution is not possible unless compressed air is available.

FIG. 2 shows the solution of the present invention in a first embodiment. The same or similar components are denoted with the same reference signs.

According to the invention, a connection 18 of the shaft feedthrough 16 is connected to the inlet 12 of the vacuum pump 10. An underpressure P₂ is therefore applied to the connection 18 of shaft feedthrough 16. In particular, P₃≥P₁>P₂ applies. Process gas flowing through the shaft feedthrough 16 is thus suctioned off through the connection 18 due to the underpressure P₂. At the same time, a barrier gas is suctioned from the drive chamber 20 to the connection 18 due to the underpressure P₂, so that process gases cannot enter the drive chamber 20. The direction of the gas flow is indicated by the arrows in FIG. 2 .

Furthermore, a first throttle is provided between the drive chamber 20 and the connection 18 of the shaft feedthrough. The first throttle 26 prevents leakage from being conveyed through the drive chamber 20 and through the vacuum pump 10 due to the restriction of the gas flow by the first throttle 26. Furthermore, a second throttle 24 is provided between the outlet 14 of the vacuum pump 10 and the connection 18 of the shaft feedthrough 16 for restricting the gas flow from the outlet 14 of the vacuum pump 10 to the inlet 12.

As can be seen from FIG. 2 , the flow direction of the flushing gas is exactly reversed when compared to the prior art. This also prevents process gas from entering the drive chamber. However, this is achieved without an additional compressed air connection, resulting in a reduction in installation costs of the vacuum pump as well as in operating costs and a simultaneous improvement of the operational reliability of the vacuum pump.

FIG. 3 shows a further embodiment of the present invention. In this case, the outlet of the connection 18 of the shaft feedthrough 16 is connected to a further vacuum pump 28 which generates the underpressure P₂ at the connection 18 of the shaft feedthrough 16 for generating the flushing gas flow in the shaft feedthrough. The further vacuum pump 28 can be designed to be significantly smaller than the vacuum pump 10. In this case, the further vacuum pump 28 can convey against the atmosphere. Alternatively, the outlet of the further vacuum pump 28 is connected to the outlet of the vacuum pump 10, so that process gases that are conveyed from the outlet 14 of the vacuum pump 10 through the shaft feedthrough 16 to the connection 18 and then through the further vacuum pump 28 cannot escape into the environment but can be fed back into the vacuum system.

FIG. 4 is a detailed view of the shaft feedthrough in the vacuum pump 10. The vacuum pump 10 has a housing 30, wherein a pump chamber 32 and a drive chamber 34 are defined by the housing 30. Furthermore, a rotor 36 is arranged in the housing 30 and is rotatably mounted by means of bearings 38. In this case, the rotor 36 has at least one rotor element in the pump chamber 32 for conveying a process gas from an inlet 12 (not depicted) to an outlet 14. For example, a transmission, an electric motor, a drive belt or the like is furthermore arranged in the drive chamber 34.

In addition, a shaft feedthrough 16 is provided which, in the example shown in FIG. 4 , is designed as a piston ring seal. In this case, the shaft feedthrough 16 has a connection 18 which is connected to an underpressure. A first throttle is generated by a first part 42 of the shaft feedthrough 16 between the drive chamber 34 and the connection 18. A second throttle is formed by a second part 40 of the shaft feedthrough 16 between the pump chamber 32 and the connection 18. In this case, an underpressure P₂ is applied to the connection 18. A pressure P₁ prevails in the drive chamber 34, which usually corresponds to atmospheric pressure. In the pump chamber 32 in the region of the shaft feedthrough 16, a pressure P₃ prevails which is usually higher than atmospheric pressure, so that the vacuum pump 10 can convey against the atmosphere. In this case, P₂<P₁≤P₃ applies. Due to the underpressure P₂ at the connection 18, a barrier gas is thus suctioned in from the drive chamber 34 through the first throttle, formed by the first part 42 of the shaft feedthrough 16, and thus prevents the process gas from escaping from the pump chamber 32 into the drive chamber 34. In particular, the shaft feedthrough 16 is designed to be contact-free and therefore requires little maintenance. Furthermore, an additional compressed air connection for the operation and prevention of process gas escaping into the environment is not required. This simplifies the structure.

In a further embodiment shown in FIG. 5 , a vacuum pump system 50 is described. In this case, the vacuum pump system 50 in the example shown has three vacuum pumps 10, all of which having shaft feedthroughs according to FIG. 2-4 . The vacuum pumps 10 are connected in parallel, so that the inlets 12 of the vacuum pumps 10 are connected to form a common inlet 52. The respective outlets 14 of the vacuum pumps 10 are also connected to one another to form a common outlet 54. The respective connections 18 of the shaft feedthroughs 16 of the respective vacuum pumps 10 are in this case connected to one another to form a common connection 56. The common connection 56 can in this case be connected to a further vacuum pump (not depicted) for generating an underpressure or, alternatively, as shown in FIG. 5 , connected to the common inlet 52, so that the underpressure at the common inlet 52 is used to generate a flushing gas from the respective drive chamber of the respective vacuum pump 10 to the respective connections 18 of the shaft feedthroughs 16.

For this purpose, the respective inlets 12 of the vacuum pumps 10 are each connected to the common inlet 52 via a check valve 58. If the vacuum pump system is, for example, in an operating state in which one of the vacuum pumps is switched off, the pressure in the deactivated vacuum pump 10 rises and lies above the pressure of the common inlet 52, and the corresponding check valve 58 closes, so that a conveying through the deactivated vacuum pump is prevented.

The present invention provides a vacuum pump and a vacuum pump system in which process gases are reliably prevented from escaping into the environment. In particular, the underpressure generated by the vacuum pump itself or an underpressure generated by a further vacuum pump is used for this purpose. In this case, the flow direction of the barrier gas within the shaft seal is reversed when compared to known shaft seals from the prior art.

Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims. 

1. A vacuum pump having: a housing which defines a pump chamber and a drive chamber, a rotor arranged in the housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet, wherein the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber, wherein the shaft feedthrough has a connection, wherein the connection is connected to an underpressure, so that a barrier gas flows from the drive chamber at least partially through the shaft feedthrough to the connection.
 2. The vacuum pump according to claim 1, characterized in that a pressure P₁ prevails in the drive chamber and the underpressure has a pressure P₂, wherein P₂<P₁, wherein in particular P₁ corresponds to atmospheric pressure.
 3. The vacuum pump according to claim 1, characterized in that a pressure P₃ prevails in the pump chamber at the shaft feedthrough and the underpressure has a pressure P₂, wherein P₂<P₃, and in particular P₃≥P₁>P₂ applies.
 4. The vacuum pump according to claim 1, characterized in that the connection is connected to a further vacuum pump for generating the underpressure.
 5. The vacuum pump according to claim 1, characterized in that the connection is connected to a vacuum portion of the pump chamber.
 6. The vacuum pump according to claim 5, characterized in that the vacuum portion of the pump chamber corresponds to the inlet of the vacuum pump.
 7. The vacuum pump according to claim 1, characterized in that a first throttle is arranged between the drive chamber and the connection.
 8. The vacuum pump according to claim 7, wherein the first throttle is formed by a first portion of the shaft feedthrough, in particular designed as a contact-free shaft seal.
 9. The vacuum pump according to claim 1, characterized in that a second throttle is arranged between the pump chamber and the connection.
 10. The vacuum pump according to claim 9, wherein the second throttle is formed by a second portion of the shaft feedthrough, in particular designed as a contact-free shaft seal.
 11. A vacuum pump system having a first vacuum pump and at least one second vacuum pump, wherein each vacuum pump has the following: a housing which defines a pump chamber and a drive chamber, a rotor arranged in the housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet, wherein the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber, wherein the shaft feedthrough has a connection, wherein the connection is connected to a common inlet of the first vacuum pump and the at least second vacuum pump or to a common further vacuum pump, so that one barrier gas each flows from the respective drive chamber through the respective shaft feedthrough.
 12. The vacuum pump system according to claim 11, characterized in that the outlet of the first vacuum pump is connected to the inlet of the second vacuum pump for the serial arrangement of the vacuum pumps.
 13. The vacuum pump system according to claim 11, characterized in that the inlet of the first vacuum pump is connected to the inlet of the at least one second vacuum pump and the outlet of the first vacuum pump is also connected to the outlet of the at least one second vacuum pump for the parallel arrangement of the vacuum pumps.
 14. The vacuum pump system according to claim 13, characterized in that a check valve, which closes when the pressure in the respective vacuum pump is higher than at the common inlet, is arranged between each vacuum pump and the common inlet. 